Patent GB-565981-A (GB)
Title: Improvements in or relating to the production of artificial filaments, films, foils and like materials
IPC: B29C48/08
Filed: 1943-01-04
Abstract: A fusible organic filament-forming composition is fed upwards through a liquid that is inert to and of greater density than the composition and the liquid is maintained at a temperature sufficiently high to melt the composition during its passage through the liquid; the molten composition is withdrawn from the surface of the inert liquid and is extruded to form filaments, films, foils, or other articles. The inert liquid employed may be a molten metal.  The main body of the molten metal may be enclosed in a vessel communicating at the bottom with a chamber or passage to the bottom of which solid composition can be forced by mechanical means.  The level of <PICT:0565981/IV/1> <PICT:0565981/IV/2> <PICT:0565981/IV/3> the molten composition in the melting chamber may be used to control the supply of solid composition, e.g. the rise and fall of the level may make and break an electrical contact by means of which the feeding means may be intermittently driven and stopped. Separate sources of heat under separate temperature controls may be employed for the different parts of the melting and extrusion apparatus.  The filament-forming composition may consist of or have a basis of a cellulose ester or ether, a polyvinyl compound, or a synthetic linear polyamide.  As shown in Fig. 1, the apparatus comprises a melt chamber 2, a supply chamber 1, a pump chamber 3 and a filter and spinning jet assembly 4, all enclosed in a block of insulating material 5.  The supply chamber 1 and melt chamber 2 are almost filled with a molten alloy of tin and lead melting at about 150 DEG C.  Chamber 1 contains a supply wheel 8 provided with recesses 9 adapted to receive short cylindrical rods 10 of the composition to be extruded.  Heat is supplied to the chamber by a flat heating element 13.  A shoe or ram 15 at the bottom of the chamber engages the rods of composition 10 and pushes them out of the recesses of wheel 8 so that they float upwards through passage 6 into the melt chamber 2, where they encounter a grid or perforated sheet 16 and remain until melted. Heat is supplied to the melt chamber by an electrical winding 18. The melted composition rises to the surface of the molten metal 7 and forms a pool 19 from which the molten composition is drawn for spinning or extrusion.  An atmosphere of nitrogen is maintained over the surface of the molten composition 19 by means of pipes 20 and 21, the latter being provided with a relief valve.  A float 22 carries a contact rod 23 which makes and breaks contact with rod 24.  The circuit containing rods 23, 24 may give a visual indication of the need for fresh composition and the wheel 8 may be driven by hand, or the circuit may control a motor which drives the wheel 8.  The molten composition flows over a sill 31 into a funnel 32 leading to pump 33. The pump chamber is packed with copper turnings so as to provide a high heat capacity.  The composition is forced through filter 37 to a spinning jet 38.  An alternative feeding device is shown in Fig. 3. A vertical tube 40 has an internal groove 41 on the side adjacent to the melt chamber and contains a screw 42 which is driven by wheel 45. Short cylinders of the composition 10 are fed to the top of tube 40 and when they reach the groove 41 they are forced down the tube by the screw 42.  At the bottom of the tube the shaft of the screw is enlarged so as to tilt the pieces of composition and allow them to float up passage 6.  Another form of feeding device is shown in Fig. 4.  It comprises a plunger 52 with disc 53 which enables pieces of the solid composition to be forced down the tube 51 into passage 6.